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Understanding Transposable Elements in Genetic Mobility

Explore the diversity of transposable elements in bacterial and eukaryotic genomes, with a focus on their mobility, impact on genetic sequences, and implications for genome evolution. Discover the mechanisms of transposition and the role of retrotransposons in genetic variation and disease.

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Understanding Transposable Elements in Genetic Mobility

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  1. Chapter 13: transposable elements Fig 13-1

  2. Multiple IS elements can exist at diverse sites in bacterial chromosomes and plasmids Example: IS elements in an F factor Fig 13-8

  3. Various classes of Insertion Sequence (IS) elements have been identified in E. coli Element-specific inverted DNA sequence repeats flank each element

  4. Transposons may be elaborate IS-type elements (simple) or DNA fragments with IS elements at each end Fig 13-9

  5. Individual plasmids can contain multiple transposons carrying multiple resistance genes Mobility of the transposons provides extensive mobility of the R factors Fig 13-10

  6. Insertion of a bacterial transposons usually involves duplication of DNA sequences flanking the insertion site Resembles restriction endonuclease cut Fig 13-11

  7. Two modes of transposition of a bacterial transposons Fig 13-12

  8. Replicative transposition involves cointegrate intermediate Fig 13-13

  9. One class of eukaryote transposable elements (retrotransposons) appear to be related to retroviruses Retrovirus life cycle Fig 13-14

  10. Examples of eukaryote retrotransposons All contain vestiges of retroviral genes most retain pol Fig 13-15

  11. Retrotransposons such as yeast Ty1 transpose through an RNA intermediate Fig 13-16

  12. The first transposon system identified: Ac-Ds system in corn (B. McClintock) Ac transposase can mobilize more than one transposon Fig 13-21

  13. Drosophila P elements were discovered by study of a hybrid dysgenesis syndrome Fig 13-18

  14. P-M dysgenesis is due to presence of the P element transposon in P flies Fig 13-19

  15. P-M dysgenesis is due to presence of the P element transposon in P flies Fig 13-19 • Mobilization limited to germline cells: • Normal development of somatic tissue • degenerate germ cells due to massive • genetic damage Fig 13-20

  16. P element has been engineered as a transformation vector Fig 13-22

  17. Up to ½ of human genome is transposable elements and residues Fig 13-23

  18. The human HGO gene contains numerous repetitive elements All elements are within introns (exon insertions are presumably subject to negative selection) Fig 13-24

  19. Many mutations are caused by insertions of transposable genetic elements

  20. Retrotransposon abundance accounts for enormous differences in genome sizes in different grasses Fig 13-25

  21. Some transposons display insertion site specificities that promote their accumulation in “safe havens” Fig 13-

  22. Fig 13-

  23. Fig 13-

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